Cancer is one of the most deadly threats to human health. In the U.S. alone, cancer affects nearly 1.3 million new patients each year, and is the second leading cause of death after cardiovascular disease, accounting for approximately 1 in 4 deaths. Solid tumors are responsible for most of those deaths. Although there have been significant advances in the medical treatment of certain cancers, the overall 5-year survival rate for all cancers has improved only by about 10% in the past 20 years. Cancers, or malignant tumors, metastasize and grow rapidly in an uncontrolled manner, making treatment extremely difficult.
CD19 is a 85-95 kDa transmembrane cell surface glycoprotein receptor. CD19 is a member of immunoglobulin (Ig) superfamily of proteins, and contains two extracellular Ig-like domains, a transmembrane, and an intracellular signaling domain (Tedder T F, Isaacs, C M, 1989, J Immunol 143:712-171). CD19 modifies B cell receptor signaling, lowering the triggering threshold for the B cell receptor for antigen (Carter, R H, and Fearon, D T, 1992, Science, 256:105-107), and co-ordinates with CD81 and CD21 to regulate this essential B cell signaling complex (Bradbury, L E, Kansas G S, Levy S, Evans R L, Tedder T F, 1992, J Immunol, 149:2841-50). During B cell ontogeny CD19 is able to signal at the pro-B, pre-pre-B cell, pre-B, early B cell stages independent of antigen receptor, and is associated with Src family protein tyrosine kinases, is tyrosine phosphorylated, inducing both intracellular calcium mobilization and inositol phospholipid signaling (Uckun F M, Burkhardt A L, Jarvis L, Jun X, Stealy B, Dibirdik I, Myers D E, Tuel-Ahlgren L, Bolen J B, 1983, J Biol Chem 268:21172-84). The key point of relevance for treatment of B cell malignancies is that CD19 is expressed in a tightly regulated manner on normal B cells, being restricted to early B cell precursors at the stage of IgH gene rearrangement, mature B cells, but not expressed on hematopoietic stem cells, or mature plasma cells (Anderson, K C, Bates, M P, Slaughenhout B L, Pinkus G S, Schlossman S F, Nadler L M, 1984, Blood 63:1424-1433).
The present standard of care for B-lineage leukemias may consists of remission induction treatment by high dose of chemotherapy or radiation, followed by consolidation, and may feature stem cell transplantation and additional courses of chemotherapy as needed (see the world wide web at cancer.gov). High toxicity associated with these treatments, as well as the risk of complications, such as relapse, secondary malignancy, or GVHD, motivate the search for better therapeutic alternatives. The expression of CD19 on both adult and pediatric (pre-B-ALL) B cell malignancies has led to exploiting this target for both antibody and chimeric antigen receptor (CAR)-T cell-based therapy (Kochenderfer J N, Wilson W H, Janik J E, Dudley M E, Stetler-Stevenson M, Feldman S A, Maric I, Raffeld M, Nathan D A, Lanier B J, Morgan R A, Rosenberg S A, 2010, Blood 116:4099-102; Lee D W, Kochenderfer J N, Stetler-Stevenson M, Cui Y K, Delbrook C, Feldman S A, Orentas R, Sabatino M, Shah N N, Steinberg S M, Stroncek D, Tschernia N, Yuan C, Zhang H, Zhang L, Rosenberg S A, Wayne A S, Mackall C L, 2015, Lancet 385:517-28).
A number of novel approaches to treat B cell leukemia and lymphoma have been developed, including bi-specific antibodies that link an anti-CD19 binding motif to a T cell binding motif (i.e. Blinatumomab, Blincyto® indicated for the treatment of Philadelphia chromosome-negative relapsed or refractory B-cell precursor acute lymphoblastic leukemia (ALL). To date, many of the binding moieties for CD19 employed in CAR constructs utilize a domain derived from murine antibodies. A number of these products are currently being considered for approval including those developed by Novartis and Kite Pharmaceuticals. In April of 2017 Novartis announced that CTL019 (tisagenlecleucel) received FDA breakthrough designation for treatment of adult patients with refractory or recurrent (r/r) DLBCL (diffuse large B cell lymphoma) who failed two or more prior therapies, adding this designation to that for r/r B-cell acute lymphoblastic leukemia (ALL). These indications were based on the Phase II JULIET study (NCT02445248) and the ELIANA study (NCT02435849), respectively. The JULIET trial showed and overall response rate (ORR) of 45%, with a 37% complete response (CR), and an 8% partial response (PR) at three months. In the ELIANA study, 82% of patients infused with the product achieved CR or CR with incomplete count recovery, and the relapse free survival rate at 6 months was 60%. The CAR-T product from Kite Pharmaceuticals (KTE-C19, axicabtagene ciloleucel) was granted breakthrough designation for diffuse large B-cell lymphoma (DLBLC), transformed follicular lymphoma (TFL), and primary mediastinal B-cell lymphoma (PMBCL). In the Kite ZUMA-3 phase II trial of KTE-C19 in r/r ALL, a 73% CR was reported (at 2 months or greater). All information is from company press releases. Whether antibody of CAR-T therapies are utilized, there are still a significant number of patients who are not helped by these therapies, and there is considerable room for improved therapeutic approaches.
Chimeric Antigen Receptors (CARs) are hybrid molecules comprising three essential units: (1) an extracellular antigen-binding motif, (2) linking/transmembrane motifs, and (3) intracellular T-cell signaling motifs (Long A H, Haso W M, Orentas R J. Lessons learned from a highly-active CD22-specific chimeric antigen receptor. Oncoimmunology. 2013; 2 (4):e23621). The antigen-binding motif of a CAR is commonly fashioned after a single chain Fragment variable (ScFv), the minimal binding domain of an immunoglobulin (Ig) molecule. Alternate antigen-binding motifs, such as receptor ligands (i.e., IL-13 has been engineered to bind tumor expressed IL-13 receptor), intact immune receptors, library-derived peptides, and innate immune system effector molecules (such as NKG2D) also have been engineered. Alternate cell targets for CAR expression (such as NK or gamma-delta T cells) are also under development (Brown C E et al Clin Cancer Res. 2012; 18 (8):2199-209; Lehner M et al. PLoS One. 2012; 7 (2):e31210). There remains significant work to be done with regard to defining the most active T-cell population to transduce with CAR vectors, determining the optimal culture and expansion techniques, and defining the molecular details of the CAR protein structure itself.
The linking motifs of a CAR can be a relatively stable structural domain, such as the constant domain of IgG, or designed to be an extended flexible linker. Structural motifs, such as those derived from IgG constant domains, can be used to extend the ScFv binding domain away from the T-cell plasma membrane surface. This may be important for some tumor targets where the binding domain is particularly close to the tumor cell surface membrane (such as for the disialoganglioside GD2; Orentas et al., unpublished observations). To date, the signaling motifs used in CARs always include the CD3-ζ chain because this core motif is the key signal for T cell activation. The first reported second-generation CARs featured CD28 signaling domains and the CD28 transmembrane sequence. This motif was used in third-generation CARs containing CD137 (4-1BB) signaling motifs as well (Zhao Y et al J Immunol. 2009; 183 (9): 5563-74). With the advent of new technology, the activation of T cells with beads linked to anti-CD3 and anti-CD28 antibody, and the presence of the canonical “signal 2” from CD28 was no longer required to be encoded by the CAR itself. Using bead activation, third-generation vectors were found to be not superior to second-generation vectors in in vitro assays, and they provided no clear benefit over second-generation vectors in mouse models of leukemia (Haso W, Lee D W, Shah N N, Stetler-Stevenson M, Yuan C M, Pastan I H, Dimitrov D S, Morgan R A, FitzGerald D J, Barrett D M, Wayne A S, Mackall C L, Orentas R J. Anti-CD22-chimeric antigen receptors targeting B cell precursor acute lymphoblastic leukemia, Blood. 2013; 121 (7):1165-74; Kochenderfer J N et al. Blood. 2012; 119 (12):2709-20). This is borne out by the clinical success of CD19-specific CARs that are in a second generation CD28/CD3-ζ (Lee D W et al. American Society of Hematology Annual Meeting. New Orleans, La.; Dec. 7-10, 2013) and a CD137/CD3-ζ signaling format (Porter D L et al. N Engl J Med. 2011; 365 (8): 725-33). In addition to CD137, other tumor necrosis factor receptor superfamily members such as OX40 also are able to provide important persistence signals in CAR-transduced T cells (Yvon E et al. Clin Cancer Res. 2009; 15 (18):5852-60). Equally important are the culture conditions under which the CAR T-cell populations were cultured, for example the inclusion of the cytokines IL-2, IL-7, and/or IL-15 (Kaiser A D et al. Cancer Gene Ther. 2015; 22 (2):72-78.
Current challenges in the more widespread and effective adaptation of CAR therapy for cancer relate to a paucity of compelling targets. Creating binders to cell surface antigens is now readily achievable, but discovering a cell surface antigen that is specific for tumor while sparing normal tissues remains a formidable challenge. One potential way to imbue greater target cell specificity to CAR-expressing T cells is to use combinatorial CAR approaches. In one system, the CD3-ζ and CD28 signal units are split between two different CAR constructs expressed in the same cell; in another, two CARs are expressed in the same T cell, but one has a lower affinity and thus requires the alternate CAR to be engaged first for full activity of the second (Lanitis E et al. Cancer Immunol Res. 2013; 1 (1):43-53; Kloss C C et al. Nat Biotechnol. 2013; 31 (1):71-5). A second challenge for the generation of a single ScFv-based CAR as an immunotherapeutic agent is tumor cell heterogeneity. At least one group has developed a CAR strategy for glioblastoma whereby the effector cell population targets multiple antigens (HER2, IL-13Ra, EphA2) at the same time in the hope of avoiding the outgrowth of target antigen-negative populations. (Hegde M et al. Mol Ther. 2013; 21 (11):2087-101).
T-cell-based immunotherapy has become a new frontier in synthetic biology; multiple promoters and gene products are envisioned to steer these highly potent cells to the tumor microenvironment, where T cells can both evade negative regulatory signals and mediate effective tumor killing. The elimination of unwanted T cells through the drug-induced dimerization of inducible caspase 9 constructs with chemical-based dimerizers, such as AP1903, demonstrates one way in which a powerful switch that can control T-cell populations can be initiated pharmacologically (Di Stasi A et al. N Engl J Med. 2011; 365 (18):1673-83). The creation of effector T-cell populations that are immune to the negative regulatory effects of transforming growth factor-β by the expression of a decoy receptor further demonstrates the degree to which effector T cells can be engineered for optimal antitumor activity (Foster A E et al. J Immunother. 2008; 31 (5):500-5). Thus, while it appears that CARs can trigger T-cell activation in a manner similar to an endogenous T-cell receptor, a major impediment to the clinical application of this technology to date has been limited in vivo expansion of CAR+ T cells, rapid disappearance of the cells after infusion, and disappointing clinical activity. This may be due in part to the murine origin of some of the CAR sequences employed.
The use of Blinotumomab (bi-specific anti-CD19 and anti-CD3 antibody) has shown impressive results for the gravely ill patients who have received this therapy. Nevertheless the durable remission rate is less than 40%, and at best only 50% of responders can be salvaged to hematopoietic stem cell transplant (HSCT) (see Gore et al., 2014, NCT01471782 and Von Stackelberg, et al., 2014, NCT01471782, summarized in: Benjamin, J E, Stein A S, 2016, Therapeutic Advances in Hematology 7:142-156). The requirement of patients who have received either bi-specific antibody or CAR-T therapy to subsequently undergo HSCT in order to maintain durable responses remains an area of active debate. Although high responses are reported for CD19 CAR-T trials, some even greater than 90%, if the trials are re-cast as “intent to treat” trials the number may be closer to 70% (Davis K L, Mackall C L, 2016, Blood Advances 1:265-268). The best results at 12 months post-CAR19 treatment reported show a RFS of 55% and and OS of 79% in patients who were able to receive the T cell product at the University of Pennsylvania (Maude S L, Teachey D T, Rheingold S R, Shaw P A, Aplenc R, Barrett D M, Barker C S, Callahan C, Frey N V, Farzana N, Lacey S F, Zheng A, Levine B, Melenhorst J J, Motley L, Prter D L, June C H, Grupp S A, 2016, J Clin Oncol 34, no15_suppl (May 2016) 3011-3011).
Accordingly, there is an urgent and long felt need in the art for discovering novel compositions and methods for treatment of B-ALL and other CD19-expressing B cell malignancies using an approach that can exhibit specific and efficacious anti-tumor effect without the aforementioned short comings.
The present invention addresses these needs by providing CAR compositions and therapeutic methods that can be used to treat cancers and other diseases and/or conditions. In particular, the present invention as disclosed and described herein provides CARs that may be used for the treatment of diseases, disorders or conditions associated with dysregulated expression of CD19 and which CARs contain CD19 antigen binding domains that exhibit a high surface expression on transduced T cells, exhibit a high degree of cytolysis of CD19-expressing cells, and in which the transduced T cells demonstrate in vivo expansion and persistence.